1. Field of the Invention
The present invention relates to a keypad assembly for use with a terminal, and more particularly to a keypad assembly for use with a terminal, which includes lighting elements.
2. Description of the Related Art
Generally, a keypad assembly of a conventional portable terminal, including without limitation portable, wireless communication terminals, comprises a keypad and a switch substrate. The keypad includes a plate-shaped elastic layer and a plurality of key buttons. The plurality of key buttons is formed on a first surface of the elastic layer. In the keypad, letter, numbers and characters, etc., are respectively printed on a surface of each key button. The switch substrate has a plurality of switches integrated therewith to provide electric contact as each key button is pushed. The switch substrate converts a depression of a respective key button into an electric signal.
The portable terminal has lighting elements enabling a user to use the keypad in the dark. A plurality of light emitting diodes and inorganic electro luminescence are used as the lighting elements. The light emitting diodes are generally arranged on a printed circuit board, while the inorganic electro luminescence is inserted in an elastic pad.
FIG. 1 is a sectional view of a conventional keypad assembly 100 including a plurality of light emitting diodes. Referring to FIG. 1, the conventional keypad assembly 100 includes a switch substrate 120, a plurality of diodes 122 and a keypad 110.
The keypad 110 includes a plate-shaped elastic layer 111, a plurality of key buttons 112, and a plurality of protrusions 111a formed on a second surface of the elastic layer 111 opposite to the first surface. Characters and the like are printed on a first surface of each key button 112. Each key button 112 and the corresponding protrusion 111a are aligned vertically.
The switch substrate 120 includes a plate type printed circuit board 120a and a plurality of switches 121. The plurality of switches 121 is formed on an upper surface of the printed circuit board 120a while being opposed to the keypad 110. Each switch 121 includes a conductive contact member and a conductive dome fully covering the contact member. The light emitting diodes 122 are mounted on the upper surface of the printed circuit board 120a. 
In order to ensure operation of the switch 121, each light emitting diode 122 is preferably prevented from being located in vertical alignment with a corresponding key button 112. That is, the light emitting diodes 122 are respectively placed between the switches 121, so as to emit the light to the respective key buttons 112 at an oblique angle. This in turn causes the light to unevenly reach each key button 112. Therefore, the respective key buttons may be shaded in darkness.
In order to solve the above-mentioned problem, some conventional keypad assemblies have been proposed which includes a keypad having an elastic layer and inorganic electro luminescence inserted in the elastic layer. However, a separate AC electric source is necessary in order to use the inorganic electro luminescence. That is, such a keypad assembly requires an inverter for converting DC to AC. As a result, the volume and manufacturing cost of the keypad assembly increases. In addition, DC to AC conversion generates noise in the portable terminal.